Seventh Chords

Why This Matters

Seventh chords are where harmony gets interesting—and where music theory exams get more demanding. You're being tested on your ability to recognize chord quality by analyzing intervals, understand how different seventh chords function within progressions, and explain why certain chords create tension while others feel stable. These concepts connect directly to harmonic analysis, voice leading, figured bass, and functional harmony—all core skills you'll need throughout your theory studies.

Don't just memorize the four notes in each chord type. Know why a dominant seventh creates tension (hint: it's the tritone), how chord quality changes when you alter just one interval, and when each chord type typically appears in common progressions. The difference between a half-diminished and fully diminished seventh chord isn't just academic—it determines how the chord functions and where it wants to resolve.

---

Stable Seventh Chords: Tonic Function

These chords can serve as points of rest in a progression. Their stability comes from consonant intervals and the absence of the tritone that drives resolution.

Major Seventh Chord

• Built from root, major third, perfect fifth, and major seventh—the most consonant of all seventh chord types
• Notated as "Maj7" or "Δ7" in lead sheets; creates a lush, sophisticated sound common in jazz and pop ballads
• Functions as a tonic chord (I) in major keys, providing color without sacrificing stability

Minor Seventh Chord

• Built from root, minor third, perfect fifth, and minor seventh—all intervals are either perfect or minor, creating a soft, mellow quality
• Notated as "m7" in chord symbols; the most common seventh chord in popular music
• Functions as tonic (i) in minor keys or as ii, iii, or vi in major keys—extremely versatile

---

Tension Chords: Dominant Function

These chords demand resolution. The tension comes from the tritone interval formed between the third and seventh of the chord, which pulls strongly toward the tonic.

Dominant Seventh Chord

• Built from root, major third, perfect fifth, and minor seventh—the combination of major third and minor seventh creates the defining tritone
• Notated simply as "7" (no prefix); the most important chord for establishing key and creating harmonic motion
• Resolves to tonic by half-step voice leading—the third rises to tonic, the seventh falls to the third of the tonic chord

Fully Diminished Seventh Chord

• Built from root, minor third, diminished fifth, and diminished seventh—stacked minor thirds create maximum instability
• Notated as "dim7" or "°7"; contains two tritones, making it extremely tense
• Symmetrical structure means any note can function as the root—$B°7$, $D°7$, $F°7$, and $A♭°7$ contain the same pitches enharmonically

---

Predominant Function: Setting Up the Dominant

These chords typically appear before dominant chords, creating the classic ii–V–I motion. Their mild tension creates forward momentum without demanding immediate resolution.

Half-Diminished Seventh Chord

• Built from root, minor third, diminished fifth, and minor seventh—only one tritone (between root and ♭5)
• Notated as "m7♭5" or "ø7"; commonly functions as ii° in minor keys or vii° in major keys
• Less unstable than fully diminished because the minor seventh is a half-step larger than the diminished seventh

---

Special Cases: Hybrid Qualities

Some seventh chords combine qualities in unexpected ways, creating unique colors for specific musical situations.

Minor-Major Seventh Chord

• Built from root, minor third, perfect fifth, and major seventh—the clash between minor third and major seventh creates a distinctive, unstable sound
• Notated as "m(Maj7)" or "mΔ7"; relatively rare but iconic in jazz and film music
• Often appears as a passing chord or as tonic in minor with an ascending chromatic line (i → i(Maj7) → i7)

---

Building and Voicing Seventh Chords

Understanding construction principles helps you identify and write any seventh chord quickly.

Chord Construction and Intervals

• All seventh chords stack thirds above a root—the quality of each third (major = 4 half-steps, minor = 3 half-steps) determines the chord type
• Interval from root to seventh is the quickest identifier: major seventh = 11 half-steps, minor seventh = 10, diminished seventh = 9
• Memorize the interval pattern for each type rather than individual note spellings—this lets you build any chord from any root

Chord Inversions

• Four possible positions for seventh chords: root position, first inversion (3rd in bass), second inversion (5th in bass), third inversion (7th in bass)
• Figured bass symbols: $7$ = root position, $6/5$ = first inversion, $4/3$ = second inversion, $4/2$ = third inversion
• Third inversion creates strong bass motion—the seventh in the bass resolves down by step, ideal for smooth voice leading

---

Functional Harmony: Chords in Context

Common Progressions Using Seventh Chords

• ii7–V7–I(Maj7) is the foundational jazz progression—predominant to dominant to tonic, all with sevenths for color
• Seventh chords on V always resolve to I; the tritone resolution is the engine of tonal music
• Secondary dominants (V7/V, V7/ii, etc.) use dominant seventh quality to tonicize chords other than I

Chord Symbols and Notation

• Lead sheet symbols provide quick shorthand: letter = root, suffix = quality (Maj7, m7, 7, ø7, °7)
• Roman numeral analysis shows function: uppercase = major triad base, lowercase = minor triad base, superscript = inversion
• Know both systems—lead sheets for performance, Roman numerals for analysis

---

Quick Reference Table

---

Self-Check Questions

1. Both the dominant seventh and half-diminished seventh contain a tritone. What distinguishes their typical harmonic functions, and on which scale degrees do they naturally occur?

2. You see the chord symbol "Cø7" on a lead sheet. What four notes would you play, and how does this chord differ from C°7?

3. Compare the interval structure of a major seventh chord and a dominant seventh chord. Which single interval is different, and how does this change the chord's stability?

4. If you're analyzing a ii–V–I progression in C minor, what seventh chord qualities would you expect on each Roman numeral? Write out the chord symbols.

5. A fully diminished seventh chord built on B contains the same pitches as diminished seventh chords built on three other roots. Name them and explain why this symmetry occurs.